Microwave cyclotron resonance of two-dimensional holes in GaAs/AlGaAs quantum wells on (100) substrates

Cyclotron resonance at microwave frequencies is used to measure the band mass ($m_b$) of two-dimensional holes (2DH’s) in the GaAs/Al$_x$Ga$_{1-x}$As quantum wells grown on (100) GaAs substrates [1]. The measured $m_b$ shows strong dependences on both the 2DH density ($p$) and the well width ($W$). For a fixed $W$, in the density range (0.4$\times10^{11}$ to 1.1$\times10^{11}$cm$^{-2}$) studied here, $m_b$ increases with $p$, consistent with previous studies of the 2DH’s on the (311)A surface [2]. However, the density dependence is significantly weaker on the (100) surface than that on the (311)A surface for the same well width of 30nm. For a fixed $p$ = 1.1$\times10^{11}$cm$^{-2}$, $m_b$ increases from 0.22$m_e$ at $W$ = 10nm to 0.54 $m_e$ at $W$ = 20nm, and stays around 0.51$m_e$ for $W$ up to 1000nm. With the transport measurement at 0.3K in the dark, the DC scattering time $\tau_{DC}$ deduced for $p$ = 1.1$\times10^{11}$cm$^{-2}$ shows a maximum of 0.6ns at $W$ = 20nm. [1] M. J. Manfra $et$ $al.$, Appl. Phys. Lett. 86, 16 (2005). [2] W. Pan $et$ $al.$, Appl. Phys. Lett. 83, 3519 (2003).